Heathers screens during the season Teenage Kicks, which runs at BFI Southbank throughout August 2014.

“I was gonna do a movie after Heathers and I got fired because the director saw Heathers and didn’t want to work with anyone associated with the movie.” – Winona Ryder

Heathers (1988) is an atypical teen movie. Its script was created by a first-time film writer working in a video store, its female lead was begged by her agent not to star in it and at least one member of its cast (Shannen Doherty) didn’t know it was a comedy until she saw the finished film.

Although high-school cliques have been portrayed in film elsewhere (most memorably in genre classics Clueless (1995) and Mean Girls (2004)), Michael Lehmann’s movie focuses on a group whose bullying, manipulation and disdain for fellow pupils is unprecedented in US teen films. To place the caustic, uncompromising behaviour in context, Andie may be treated shamefully by the rich kids in Pretty in Pink (1986) but they’re like bosom buddies compared to the Heathers.

The story focuses on clique fringe player Veronica Sawyer as she becomes disillusioned with the titular trio and plots their downfall with enigmatic outsider Jason Dean (J.D.). If such a plot sounds thin, what is done with such a simple idea is often brilliant and consistently hilarious.

Distributor New World Pictures closed weeks after its release so the film’s marketing budget was almost non-existent. This and the film’s pitch-black tone and content meant the movie made just $1.1m, a little over half its budget. However, while Heathers flopped at the box office it eventually amassed a huge cult following – one it retains more than 25 years later. Here are seven reasons why.

1. Winona takes it all

Heathers (1988)

Thankfully for her and us, Ryder ignored her agent’s advice, took the part in Heathers and swiftly ditched the doubtful agent. She is terrific in her career-best role as Veronica. Anxious and angry, frightened and steadfast, confident and conflicted – she’s torn between old friends, the lure of popularity and the magnetic J.D. She’s also somehow the moral compass of the film, despite committing murder. It’s worth watching Heathers just for Veronica’s narration. When she talks about her teenage angst she says: “This isn’t just a spoke in my menstrual cycle.” She’s flawed, is too easily led by bad influences, and vomits in a university dorm hallway – but you can’t help but admire her.

2. Dialogue to die for

The dialogue in Daniel Waters’ brisk, mordant script is arguably the greatest individual component of Heathers. Waters claims that he gave the pretty, wealthy, powerful clique their idiosyncratic expressions so the film wouldn’t date, as it would have done if he had used contemporary slang. While this may be true, the insults and banter also sound a lot like any normal bunch of friends (albeit more consistently creative and funny), so maybe his own pals were an influence. His script offers a masterclass in adolescent cruelty. Clique leader Heather Chandler utters many of the best lines, including the deathless, “Did you have a brain tumour for breakfast?” and “Grow up Heather, bulimia’s so ’87.”

3. Christian Slater

There is no escaping it, Christian Slater talks and acts a lot like Jack Nicholson. Lehmann even told him during the shooting of one scene to play it less like Nicholson until he realised that it was the natural rhythm and cadences of Slater’s speech that made him sound that way, rather than any deliberate attempt to mimic the actor. J.D. is a character one can imagine a young Nicholson playing with relish. He’s a good-looking rebel with a smart mouth, a taste for mischief, and murderous intentions. Although the role doesn’t quite call for the manic energy of Slater’s pirate radio DJ in Pump Up the Volume (1990), his screen presence, intelligence and charm is undeniable. As the film develops and J.D.’s psychopathic tendencies become more pronounced, he is never less than convincing.

Heathers (1988)

4. Controversy

Heathers doesn’t shy away from controversial topics. Teenage suicide, bulimia, date rape, homosexuality, religion, hypocrisy, cynicism, sex and murder are all tackled (as well as the lesser-known rural recreation of cow tipping). But despite the film being so packed with weighty issues it never feels glib. There’s a great deal of truth amid the serious topics but because it’s all delivered stuffed inside incisive jokes viewers never feel like they’re being preached to or patronised.

5. Small is beautiful

One or both of Slater and Ryder may be in almost every scene but there are also a few supporting roles worth watching out for. Principal Gowan (John Ingle) may not have as much to do as Richard Vernon in The Breakfast Club (1985) or Edward Rooney in Ferris Bueller’s Day Off (1986) but his stewardship of Westerburg High is amusingly cynical. His colleague Pauline Fleming (Penelope Milford), meanwhile, is a new-age pedagogue who makes the pupils join hands and discuss their feelings. As teachers go, she’s as ludicrous as Kitty Farmer in Donnie Darko (2001), though much less threatening. Glenn Shadix, who like Ryder was fresh from a role in Beetlejuice (1988), also has a short but memorable turn as OTT priest Father Ripper.

Heathers (1988)

6. How it looks

Cinematographer Francis Kenny and editor Norman Hollyn called each other every day while making Heathers to express their pride in producing brilliant looking scenes and visually inventive cuts. Kenny’s work is understated and helps reinforce the film’s tonal descent. At the start there are vivid colours in abundance but as the film wears on, the hues on screen darken as the plot does. Hollyn’s editing meanwhile gives the film its snappy pace and lets the camera linger on Veronica as she becomes more and more unsettled by J.D.’s unsavoury actions.

7. Know the score

As the brother of fellow composer Thomas Newman (The Lost Boys, 1987; The Shawshank Redemption, 1994) and the cousin of Randy (the Toy Story trilogy, 1995-2010), David Newman’s musical pedigree is beyond reproach. Here his synth-heavy score is often ominous but never overblown. At its best it recalls the work of German ambient/electronica wizards Tangerine Dream, appropriately enough given that it features several moments of unreal, dreamlike calm that lull viewers into a false sense of security while the action on screen becomes more chaotic.